In conventional technologies, it is assumed that shape errors in a corner portion occur due to the deflection of the wire and measures, such as adjusting the discharge power, increasing the tension, using dwell, and performing trajectory control, to correct the deflection of the wire, are taken in order to reduce the deflection of the wire during corner machining as a method of improving the rough machining corner accuracy (see Patent Literatures 1 and 2).
Moreover, as a method of improving the corner accuracy during finish machining, there are a method (see Patent Literatures 3 and 4) in which speed control is performed in accordance with the change of the amount of machining in the corner portion and a method (see Patent Literature 5) in which the change of the amount of machining is estimated before the corner portion is machined and a correction is made for the change of the side surface gap of the wire electrode in the corner portion on the basis of the estimation result.